Steering nozzle modification

[CrankyGypsy]

(referencing 2008 Sea Doo Challenger 180)

I ran across a post on another forum a while back that I can't currently find. The owner used a piston cylinder honing tool to remove the "steps" inside the steering nozzle. I'm not sure which models of PWC/boats have these steps. It is believed these steps, which shape the circular nozzle into an oval nearest to the pump venturi, is a safety feature that slows the craft during turns.

I tried the honing tool, but found the three legs did not allow for an even removal of material where it was needed - a four-legged version may work better?
So, I smoothed-out these steps by first cross-hatching them with a grinding wheel to quickly remove material, then using a rotary burr bit to shape the contour, followed with 80grit and 120grit to smooth it out.



My tests seem to have improved turning g-forces slightly. Where it was more noticeable to me, was coming out of a turn: the boat seems to recover more quickly to get back up to speed. I didn't take the time to "port" the contour to be perfectly round (that's a lot of material to remove), so more performance may be possible. I plan to eventually repaint the inside with VHT Satin Black Epoxy Paint.

 

[Gym]

Interesting @CrankyGypsy. I'm wondering if those internal ribs play a dual role. Is it possible they also add strength to the nozzle?

 

[CrankyGypsy]

Is it possible they also add strength to the nozzle?

Hadn't considered that, but it's a fairly beefy part throughout - I can't imagine the steps being necessary for that purpose. Here is a photo I found of one that fits a 2013+ GTR and another pic of a 1995-era nozzle showing that the additional girth was not present, even with a thinner wall (note: there are similar ones from that era that do not have the center low-speed rudder, either). If I were to remove the steps entirely (and accurately), the width in these areas would still be 3/16" like the rest of the nozzle. I've been looking for different angled pics of aftermarket nozzles and from what little I could find, they do not appear to have the steps ...however, their literature does not explicitly say they don't.



A quick Google Image search has me believing modern Sea Doos all have these "safety" steps ...probably there to inhibit spins that can result in high-sides.

All of this speculation on my part is probably already common knowledge over at GreenHulk - I just couldn't find anything with my searches.

 

[Julian]

I'm trying to understand how these steps would inhibit you from spinning the boat? Do you feel a difference? Can you explain what the effect is?

Seems to me that they are far more likely one of 2 things:

1. Intentionally put there to add rigidity to the nozzle
2. There unintentionally as part of the manufacturing process

My bet would be #2. Seadoo put the part out to bid, some fabricator met their spec with this design and that was it. No one bothered to think that it might cause turbulence in the outflow (but would it really?) I think the intake side of the pump is far more important than the output in terms of disturbing water flow.....

I doubt what you've done has any negative impact....as for positive impact....that would be very hard to test accurately.

 

[Cambo]

Did you read this thread

https://jetboaters.net/threads/pump-intake-grates-thinking-of-trying-something-taboo.15594/

Maybe do this as well for super smooth water flow and max pump loading My 2005 had a cleaner transition than the 2017. On the 2005 I went in and re siliconed cleaned up the impeller edges and it helped eliminate some cavitation that was occuring with a heavy load.

 

[CrankyGypsy]

I'm trying to understand how these steps would inhibit you from spinning the boat? Do you feel a difference?
I doubt what you've done has any negative impact....as for positive impact....that would be very hard to test accurately.

I believe you would understand if you could see the relation of the venturi to the nozzle, first hand. As you turn the nozzle, the output of the venturi is directed at this step ...once you hit the steering stop, the step is practically "down stream" of the flow of water. This certainly results in turbulence. Once I realized this, I could understand the relation as I got more aggressive with the turn during a high speed run. Once the flow is no longer hitting that step, the boat immediately picks back up ...it is now picking up quicker with the reduction of these steps. As for the design/manufacturing of the nozzle, I would disagree with both: 1) no need for increased strength - 3/16" is strong enough as that is the thickness where the mounts are and previous generation of nozzle appear to be thinner; 2) wasted materials.

Keeping in mind I have little PWC experience: compared to a PWC, the boat is certainly not as easy to spin due to the mass. I could see running a PWC beyond 50mph and gradually making the turn to maintain that speed. If the nozzle is manipulated smoothly enough, I could imagine the PWC continuing to plane and eventually the turning radius would easily jettison an inexperienced rider (via g-force or high-side from cutting the throttle).

Did you read this thread

Yup, I'm post #107. I haven't tried running without the grate, yet (which seems to have been abandoned in that thread). I'm not sold on a top-loader idea because Sea Doo didn't bothered with it from the outset - I think I remember reading somewhere where it is believed the boats do a better job at introducing enough water to the pump and too much pump-loading can be detrimental. They did redesigned the hull in 2009 for improved pump loading, however ...that is why I wonder if removal could give a smoother introduction (though some argue the grates actually help direct water in). I'm still working bugs out of issues due to the previous owner while I also mess with this and the porpoising issue, which is another issue they addressed via the hull in 2009.

The design of the Ride Plate is a little strange by Yamaha standards: it actually isn't sealed all the way around. It has lead me to be less concerned with cavitation caused by sealing, and I sealed the heck of my AR230. Besides, I'm not feeling cavitation and my boat seems to top-out on the higher end of most C180 owner's max MPH. I know there are spots I can seal up to reduce drag, but that is also on the back burner, right now.

Maybe I underplayed the results I got too much - am I ecstatic with them? Not as much as I might be had it been my first boat, because the twin MR-1s on my AR230HO hooked-up like AWD compared to this single-engine C180. I am not gonna say that pump-loading or cavitation isn't part of the problem (I'm not convinced either of those are a problem at all with this boat), but the "obtrusive" nozzle step is playing the major role.
Would I grind them off my next Sea Doo? Yes.

 

[Cobra Jet Steering LLC]

ha I put steering on my nozzles and I never slip or slide I can jump a wake land behind the boat and turn back to the side I came in from effortlessly